1. noun.
The gap between two soft entities on the body. Usually the cleft between a womans breasts. Also sometimes used to describe the anus' "Butt Cleavage", or even out of the ordinary, fat caused cleavage in other parts of the body such as the side rolls, or even "chin cleavage"... burr.

2. noun.
Any gap caused by an axe or wedge shaped (cleaver) object.

3. verb.
The act of cutting or slicing your enimies. Done with a meat cleaver or any wedge, one can deal out "unnatural" cleavage to whomever they please, male OR female. To have cleavage in this case means to have the ability for cutting and slicing.

"Oh God I love that Cleavage!"

"As you can see, this phenominon left many cleavages in the rock formation here."

The area that is viewed either between breasts, or preferably at the contact point between breasts. Often one of the determining factors when the male mind subconsciously rates a woman on the bang-ability scale. Less cleavage is preferred when titty fucking. Often women will expose their cleavage when leaning forward in order to appear desirable, although this should only be done with firm, well rounded breasts.
Some times (though rarely) referred to as the "Boob border"

"You know, I have to be honest. I may love her for who she is, but I have to admit that i fantasise about getting a titty fuck from Caitlin."

"In my opinion Joelle's cleavage should be elected president."

"Dude, I wish sexual harassment wasn't against the law. I would die happily drowning in Kait's cleavage."